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At least 559 records · Page 31Linked to original sources
USGS2006

Effects of southern flying squirrels Glaucomys volans on red-cockaded woodpecker Picoides borealis reproductive success

Anecdotal data gathered from many populations suggest that southern flying squirrel (SFS, Glaucomys volans ) use of the endangered red-cockaded woodpecker's (RCW, Picoides borealis ) nest and roost cavities may negatively affect RCW populations. We conducted a controlled experiment to determine the effects of SFSs on RCW reproductive success. During the 1994 and 1995 breeding seasons, SFSs were removed from 30 RCW clusters and 32 clusters served as controls. SFSs were the most frequently encountered occupants of RCW cavities and used 20–33% of RCW cavities in control and treatment clusters over both years. Treatment groups produced significantly more successful nests (≥ 1 fledgling) than control groups in 1994. In 1995 however, there was no difference in the number of successful nests. In both years, RCW groups nesting in treatment clusters produced significantly more fledglings than groups in control clusters in each of four experimental areas, averaging approximately 0.7 additional fledglings per nesting group. Loss of entire clutches or broods, possibly as a result of predation or abandonment, was a major factor limiting reproduction in control groups in 1994. In contrast, differences in partial brood loss appeared to be the cause of differential fledging success in 1995. Usurpation of RCW roost cavities by SFSs may have placed greater energetic demands on RCWs for cavity defence or thermoregulation, thus reducing energy available for reproduction. Our results show that SFS use of RCW cavities during the breeding season has a significant impact on RCWs and that management of RCW populations should include activities that either minimize SFS populations in RCW clusters or limit access of SFSs to RCW cavities.

Animal Conservation↗
USGS2005

Application of a nonlinear slug test model

Knowledge of the hydraulic conductivity distribution is of utmost importance in understanding the dynamics of an aquifer and in planning the consequences of any action taken upon that aquifer. Slug tests have been used extensively to measure hydraulic conductivity in the last 50 years since Hvorslev's (1951) work. A general nonlinear model based on the Navier-Stokes equation, nonlinear frictional loss, non-Darcian flow, acceleration effects, radius changes in the wellbore, and a Hvorslev model for the aquifer has been implemented in this work. The nonlinear model has three parameters: β, which is related primarily to radius changes in the water column; A, which is related to the nonlinear head losses; and K, the hydraulic conductivity. An additional parameter has been added representing the initial velocity of the water column at slug initiation and is incorporated into an analytical solution to generate the first time step before a sequential numerical solution generates the remainder of the time solution. Corrections are made to the model output for acceleration before it is compared to the experimental data. Sensitivity analysis and least squares fitting are used to estimate the aquifer parameters and produce some diagnostic results, which indicate the accuracy of the fit. Finally, an example of field data has been presented to illustrate the application of the model to data sets that exhibit nonlinear behavior. Multiple slug tests should be taken at a given location to test for nonlinear effects and to determine repeatability.

Ground Water↗
USGS2007

Experimental Marvin Windshield Effects on Precipitation Records in Leadville, Colorado

An evaluation of the Leadville, Colorado, precipitation records that include a reported record-breaking storm (and flood) at higher elevations in the Rocky Mountains has indicated that the use of an experimental Marvin windshield (designed to decrease the effects of wind on precipitation-gage catchment of snow during winter) resulted in substantially overregistered summer precipitation for 1919 to 1938. The July monthly precipitation for these years was over-registered by an average of 157 percent of the long-term July monthly precipitation at Leadville. The cause of the overregistration of precipitation was the almost 4-foot-top-diameter cone-shaped windshield that had the effect of 'funneling' hail and rain splash into the rain gage. Other nearby precipitation gages, which did not use this Marvin windshield, did not have this trend of increased precipitation for the same period. Streamflow records from the Leadville area also do not indicate an increase in streamflow from 1919 to 1938.

Water Resources Bulletin↗
USGS2009

An enriched stable-isotope approach to determine the gill-zinc binding properties of juvenile rainbow trout (Oncorhynchus mykiss) during acute zinc exposures in hard and soft waters

The objective of the present study was to employ an enriched stable-isotope approach to characterize Zn uptake in the gills of rainbow trout (Oncorhynchus mykiss) during acute Zn exposures in hard water (???140 mg/L as CaCO 3 ) and soft water (???30 mg/L as CaCO 3 ). Juvenile rainbow trout were acclimated to the test hardnesses and then exposed for up to 72 h in static exposures to a range of Zn concentrations in hard water (0-1,000 ??g/L) and soft water (0-250 ??g/L). To facilitate detection of new gill Zn from endogenous gill Zn, the exposure media was significantly enriched with 67 Zn stable isotope (89.60% vs 4.1% natural abundance). Additionally, acute Zn toxicity thresholds (96-h median lethal concentration [LC50]) were determined experimentally through traditional, flow-through toxicity tests in hard water (580 ??g/L) and soft water (110 ??g/L). Following short-term (???3 h) exposures, significant differences in gill accumulation of Zn between hard and soft water treatments were observed at the three common concentrations (75, 150, and 250 ??g/L), with soft water gills accumulating more Zn than hard water gills. Short-term gill Zn accumulation at hard and soft water LC50s (45-min median lethal accumulation) was similar (0.27 and 0.20 ??g/g wet wt, respectively). Finally, comparison of experimental gill Zn accumulation, with accumulation predicted by the biotic ligand model, demonstrated that model output reflected short-term (<1 h) experimental gill Zn accumulation and predicted observed differences in accumulation between hard and soft water rainbow trout gills. Our results indicate that measurable differences exist in short-term gill Zn accumulation following acclimation and exposure in different water hardnesses and that short-term Zn accumulation appears to be predictive of Zn acute toxicity thresholds (96-h LC50s). ?? 2009 SETAC.

Environmental Toxicology and Chemistry↗
USGS2019

Estimating sightability of greater sage-grouse at leks using an aerial infrared system and N-mixture models

Counts of grouse present at leks (breeding grounds) during spring are widely used to monitor population numbers and assess trends. However, only a proportion of birds available to count are detected resulting in a biased population index. We designed a study using an aerial integrated infrared imaging system (AIRIS) and experimental pseudo-leks to quantify sightability (proportion of birds detected) of conventional ground-based visual (GBV) surveys for greater sage-grouse Centrocercus urophasianus . Specifically, we calibrated AIRIS at pseudo-leks composed of known numbers of captively-raised birds, primarily ring-necked pheasant Phasianus colchicus . We then carried out AIRIS and GBV surveys, simultaneously, on nearby sage-grouse leks, allowing us to model AIRIS and GBV sightability. AIRIS detected ∼93% of birds on pseudo-leks while GBV detected ∼86% of sage-grouse on leks. Thus, the ground count observation error was –14% from the ‘true' number of male sage-grouse attending the leks. We also found sagebrush cover decreased sightability for GBV counts but did not influence sightability by AIRIS. Because standard GBV protocols typically make repeated counts of sage-grouse in a single morning, we also modeled repeated GBV counts using N -mixture models and found an 88% sightability, which was nearly the same as GBV sightability from the AIRIS analysis. This suggests that the use of repeated morning counts can potentially account for imperfect detection in the standard GBV surveys currently implemented. We also provide generalized correction values that could be employed by resource managers using either GBV or AIRIS to better estimate ‘true’ numbers of sage-grouse attending leks within similar environments to this study. The findings and interpretation presented can help guide effective monitoring protocols that account for observation error and improve accuracy of data used for population trend and abundance estimation.

California, Idaho, Nevada↗
USGS1976

Two-dimensional steady-state dispersion in a saturated porous medium

A previously developed analytical solution for two-dimensional dispersion is computed for various conditions. These results were then compared with solution of previously developed approximate models of transverse dispersion which were used to analyze experimentally derived concentration distribution. Comparison established that, whenever steady state was reached, the values of dispersion coefficient computed using the approximate expression agreed with values derived from exact expression and in addition allowed a quick computation of the parameter.

Journal of Research of the U.S. Geological Survey↗
USGS2014

Response of plant community structure and primary productivity to experimental drought and flooding in an Alaskan fen

Northern peatlands represent a long-term net sink for atmospheric CO 2 , but these ecosystems can shift from net carbon (C) sinks to sources based on changing climate and environmental conditions. In particular, changes in water availability associated with climate control peatland vegetation and carbon uptake processes. We examined the influence of changing hydrology on plant species abundance and ecosystem primary production in an Alaskan fen by manipulating the water table in field treatments to mimic either sustained flooding (raised water table) or drought (lowered water table) conditions for 6 years. We found that water table treatments altered plant species abundance by increasing sedge and grass cover in the raised water table treatment and reducing moss cover while increasing vascular green area in the lowered water table treatment. Gross primary productivity was lower in the lowered treatment than in the other plots, although there were no differences in total biomass or vascular net primary productivity among the treatments. Overall, our results indicate that vegetation abundance was more sensitive to variation in water table than total biomass and vascular biomass accrual. Finally, in our experimental peatland, drought had stronger consequences for change in vegetation abundance and ecosystem function than sustained flooding.

Alaska↗
USGS2003

Direct numerical simulation of bedload transport using a local, dynamic boundary condition

Temporally and spatially averaged models of bedload transport are inadequate to describe the highly variable nature of particle motion at low transport stages. The primary sources of this variability are the resisting forces to downstream motion resulting from the geometrical relation (pocket friction angle) of a bed grain to the grains that it rests upon, variability of the near-bed turbulent velocity field and the local modification of this velocity field by upstream, protruding grains. A model of bedload transport is presented that captures these sources of variability by directly integrating the equations of motion of each particle of a simulated mixed grain-size sediment bed. Experimental data from the velocity field downstream and below the tops of upstream, protruding grains are presented. From these data, an empirical relation for the velocity modification resulting from upstream grains is provided to the bedload model. The temporal variability of near-bed turbulence is provided by a measured near-bed time series of velocity over a gravel bed. The distribution of pocket friction angles results as a consequence of directly calculating the initiation and cessation of motion of each particle as a result of the combination of fluid forcing and interaction with other particles. Calculations of bedload flux in a uniform boundary and simulated pocket friction angles agree favourably with previous studies.

Sedimentology↗
USGS1988

Experimental oxygen isotope fractionation between siderite-water and phosphoric acid liberated CO2-siderite

The equilibrium fractionation of O isotopes between synthetic siderite and water has been measured at temperatures ranging from 33° to 197°C. The fractionation between siderite and water over this temperature range can be represented by the equation: 10 3 ln α = 3.13 × 10 6 T −2 − 3.50. Comparison between the experimental and theoretical fractionations is favorable only at approximately 200°C; at lower temperatures, they generally differ by up to 2 permil. Siderite was prepared by the slow addition of ferrous chloride solutions to sodium bicarbonate solutions at the experimental temperatures. It was also used to determine the O isotope fractionation factors between phosphoric acid liberated CO 2 and siderite. The fractionation factors for this pair at 25° and 50°C are 1.01175 and 1.01075, respectively. Preliminary results of the measured C isotope fractionation between siderite and Co 2 also indicate C isotopic equilibrium during precipitation of siderite. The measured distribution of 13 C between siderite and CO 2 coincides with the theoretical values only at about 120°C. Experimental and theoretical C fractionations differ up to 3 permil at higher and lower temperatures.

Geochimica et Cosmochimica Acta↗
USGS1996

Kinetic and mineralogic controls on the evolution of groundwater chemistry and 87Sr/86Sr in a sandy silicate aquifer, northern Wisconsin, USA

Substantial flowpath-related variability of 87Sr/86Sr is observed in groundwaters collected from the Trout Lake watershed of northern Wisconsin. In the extensive shallow aquifer composed of sandy glacial outwash, groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter-lake uplands. 87Sr/86Sr of groundwater derived mainly as seepage from a precipitation-dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase. In contrast, 87Sr/86Sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed, due to suppression of plagioclase dissolution together with preferential leaching of Sr from radiogenic phases such as K-feldspar and biotite. The results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic Sr, whereas stagnant waters obtain relatively radiogenic Sr. Nearly the entire range of strontium-isotope composition observed in groundwaters from the watershed was measured in the experimental product waters. The constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase, perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions. In contrast, episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution, perhaps due to accumulation of clay mineral nuclei on its reactive surfaces. Differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior. This study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths, and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations.

Geochimica et Cosmochimica Acta↗
USGS2024

Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide

Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77 ° K and 195 ° K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 μ in size, samples were prepared by replacing the original exchangeable cations with Li + , Na + , K + , Rb + , Cs + , Mg ++ , Ca ++ , Ba ++ , and NH 4 + , forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsorbate, ranged from 61 m 2 /g for Li-montmorillonite to 138 m 2 /g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically result in a surface area of over 300 m 2 /g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77 ° K does not penetrate the layers and provides a measure only of the external surface of expandable clay minerals. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195 ° K. Surface area values ranged from 99 m 2 /g for Li-montmorillonite to 315 m 2 /g for Csmontmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a result of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance.

Clays and Clay Minerals↗
USGS2011

Storage as a Metric of Catchment Comparison

The volume of water stored within a catchment, and its partitioning among groundwater, soil moisture, snowpack, vegetation, and surface water are the variables that ultimately characterize the state of the hydrologic system. Accordingly, storage may provide useful metrics for catchment comparison. Unfortunately, measuring and predicting the amount of water present in a catchment is seldom done; tracking the dynamics of these stores is even rarer. Storage moderates fluxes and exerts critical controls on a wide range of hydrologic and biologic functions of a catchment. While understanding runoff generation and other processes by which catchments release water will always be central to hydrologic science, it is equally essential to understand how catchments retain water. We have initiated a catchment comparison exercise to begin assessing the value of viewing catchments from the storage perspective. The exercise is based on existing data from five watersheds, no common experimental design, and no integrated modelling efforts. Rather, storage was estimated independently for each site. This briefing presents some initial results of the exercise, poses questions about the definitions and importance of storage and the storage perspective, and suggests future directions for ongoing activities.

Hydrological Processes↗
USGS2012

The challenges of implementing pathogen control strategies for fishes used in biomedical research

Over the past several decades, a number of fish species, including the zebrafish, medaka, and platyfish/swordtail, have become important models for human health and disease. Despite the increasing prevalence of these and other fish species in research, methods for health maintenance and the management of diseases in laboratory populations of these animals are underdeveloped. There is a growing realization that this trend must change, especially as the use of these species expands beyond developmental biology and more towards experimental applications where the presence of underlying disease may affect the physiology animals used in experiments and potentially compromise research results. Therefore, there is a critical need to develop, improve, and implement strategies for managing health and disease in aquatic research facilities. The purpose of this review is to report the proceedings of a workshop entitled “Animal Health and Disease Management in Research Animals” that was recently held at the 5th Aquatic Animal Models for Human Disease in September 2010 at Corvallis, Oregon to discuss the challenges involved with moving the field forward on this front.

Comparative Biochemistry and Physiology, Part C: T↗
USGS2002

Analysis of eight argonne premium coal samples by X-ray fluorescence spectrometry

X-ray fluorescence spectrometric methods were used in the analysis of eight Argonne Premium Coal Samples. Trace elements (Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, La, and Ce) in coal ash were determined by energy-dispersive X-ray fluorescence spectrometry; major elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, Mn, and Fe) in coal ash and trace elements (Cl and P) in whole coal were determined by wavelength-dispersive X-ray fluorescence spectrometry. The results of this study will be used in a geochemical database compiled for these materials from various analytical techniques. The experimental XRF methods and procedures used to determine these major and trace elements are described.

Energy & Fuels↗
USGS2026

Polystyrene microplastics alter the accumulation and elimination dynamics of silver nanoparticles in Daphnia magna

Rationale Microplastics (MPs) can interact with engineered nanomaterials and alter their environmental fate and bioavailability. However, their influence on the bioaccumulation dynamics of silver nanoparticles (AgNPs) in aquatic filter feeders under environmentally relevant conditions remains poorly understood. We hypothesized that polystyrene microplastics (PS-MPs) alter the uptake, elimination and overall bioaccumulation dynamics of AgNPs in Daphnia magna . Methodology Adult D. magna were exposed to isotopically labeled citrate-coated 109 AgNPs in the presence and absence of PS-MPs. Waterborne uptake, dietary uptake, assimilation efficiency, food ingestion and elimination were quantified experimentally and incorporated into a biodynamic model to predict steady-state silver (Ag) concentrations under environmentally relevant exposure scenarios. Results PS-MPs increased waterborne Ag accumulation by approximately eightfold compared with AgNPs exposure alone. However, Ag elimination was substantially faster, with 98% of accumulated Ag eliminated after five days of depuration compared with 66% without PS-MPs. PS-MPs also reduced food ingestion rates (IRs), while assimilation efficiency remained largely unchanged. Biodynamic modeling predicted that steady-state Ag accumulation was approximately fivefold greater in the presence of PS-MPs, with waterborne exposure becoming the dominant accumulation pathway. Discussion These findings suggest that PS-MPs alter bioaccumulation dynamics of AgNPs in filter-feeding organisms by enhancing organism-associated Ag during waterborne exposure while accelerating Ag elimination, likely through particle-associated transport and gut egestion. Collectively, these results underscore the complexity of Ag bioaccumulation processes when MPs and AgNPs interact and highlight the importance of studies conducted under environmentally relevant conditions.

Environmental Chemistry↗
USGS2006

Do females trade copulations for food? An experimental study on kittiwakes (Rissa tridactyla)

Females of many species copulate more frequently than necessary to fertilize their eggs despite the potential costs. Several studies, particularly on socially monogamous birds, have suggested that females obtain immediate material benefits by trading copulations for nutrients or other resources. We experimentally tested this hypothesis by manipulating the food resources available to prelaying female black-legged kittiwakes ( Rissa tridactyla ). If female kittiwakes trade copulations for courtship feeding because they need the extra resources, well-fed females (experimental group) should be less willing to copulate compared with females that are more food limited (control group). Contrary to our predictions, we found that close to the start of laying experimental females copulated more frequently with their mate than control females. We also observed that males from the experimental group fed their mate at least as often as males from the control group. In experimental pairs, we still observed a positive correlation between the rate of copulation and the rate of courtship feeding. Our results thus refute the immediate material benefits hypothesis. Currently available data are consistent with the hypothesis that prelaying courtship feeding is a form of mating effort. We suggest that the rate of courtship feeding might be a sexually selected trait, on which females base decisions about timing and frequency of copulations, but this remains to be tested.

Alaska↗
USGS2002

Reduction of provisioning effort in response to experimental manipulation of chick nutritional status in the Horned Puffin

Using a supplemental feeding experiment, we investigated the ability of adult Horned Puffins to decrease provisioning effort in response to reduced nutritional requirements of chicks. We found no difference between experimental and control groups in parental provisioning before supplementary feeding was initiated. After receiving supplemental food for seven days, experimental chicks grew faster, gained more mass and received 87% less food from their parents than did control chicks. These results demonstrate that Horned Puffin parents can decrease food provisioning in response to a decrease in their chick nutritional requirements.

Alaska↗
USGS2022

P- and S-wave velocity estimation by ensemble Kalman inversion of dispersion data for strong motion stations in California

This study uses an ensemble Kalman method for near-surface seismic site characterization of 154 network earthquake monitoring stations in California to improve the resolution of S -wave velocity ( V S ) and P -wave velocity ( V P ) profiles—up to the resolution depth—coupled with better quantification of uncertainties compared to previous site characterization studies at this network. These stations were part of the Yong et al . site characterization project, with selected stations based on future recordings of ground motions that are expected to exceed 10 per cent peak ground acceleration in 50 yr. To estimate V S and V P from experimental dispersion data, Yong et al . investigated these stations using linearized (local search and iteration) routines, and Yong et al . later studied a subset of these stations using nonlinear (global search and optimization) routines. In both studies, the selection of model parameters—that is, discretization of the V S and V P profiles with only five fixed thickness layers—was mainly based on trial and error. In contrast, this paper uses an approximate Bayesian method to assimilate experimental dispersion data and sequentially update an ensemble of particle estimates that span the V S and V P parameter spaces. Doing so, we systematically determine the most probable profiles conditioned on the experimental dispersion data, the introduced noise levels, and a priori knowledge in the form of physical constraints. We consider two configurations to discretize the soil depth from the surface to half of the maximum discernible wavelength obtained from the experimental dispersion data, namely refined and coarse models, and two initial models for each configuration to study solution multiplicity. Our results suggest that using the refined model for the top surface layers improves the resolution of near-surface site characteristics and the model’s success rate in capturing dispersion data at high frequencies. All models result in similar V S but distinct V P profiles, with increasing uncertainty at deeper layers, suggesting that the fundamental mode of Rayleigh wave dispersion data is not adequate to constrain the P -wave velocity profile and the S -wave velocity close to the resolution depth.

California↗